Rechargeable lithium ion batteries are included in a variety of electronic devices. Most commercially available lithium ion batteries have anodes that contain materials such as graphite that are capable of incorporating lithium through an intercalation mechanism during charging. Such intercalation-type anodes generally exhibit good cycle life and coulombic efficiency. However, the amount of lithium that can be incorporated per unit mass of intercalation-type material is relatively low.
A second class of anode material is known that incorporates lithium through an alloying mechanism during charging. Although these alloy-type materials can often incorporate higher amounts of lithium per unit mass than intercalation-type materials, the addition of lithium to the alloy is usually accompanied with a large volume change. Some alloy-type anodes exhibit relatively poor cycle life and coulombic efficiency. The poor performance of these alloy-type anodes may result from the formation of a two-phase region during lithiation and delithiation. The two-phase region can create internal stress within the alloy if one phase undergoes a larger volume change than the other phase. This internal stress can lead to the disintegration of the anode material over time.
Further, the large volume change accompanying the incorporation of lithium can result in the deterioration of electrical contact between the alloy, conductive diluent (e.g., carbon) particles, and binder that typically form the anode. The deterioration of electrical contact, in turn, can result in diminished capacity over the cycle life of the anode.